Anti-ozonant

ABSTRACT

(CYCLOHEXEN-(3)-YLIDENE-METHYL)-HYDROCARBON ETHERS AND THIOETHER AND THEIR CORRESPONDING 2,5-ENDOMETHYLENE DERIVATIVES, PREPARATION THEREOF AND THEIR USE AS ANTI-OZONANTS.

United States Patent 3,639,485 ANTI-OZONANT Roland Nast,Cologne-Buchheim, Kurt Ley, Leverkusen, Wolfgang Retletzky, Opladen, andTheo Kempermann, Cologne-Lindenthal, Germany, assignors toFarbenfabriken Bayer Aktiengesellschaft, Leverkusen, Germany No Drawing.Filed July 16, 1968, Ser. No. 745,091 Claims priority, applicationGermany, Feb. 5, 1968, F 54,738 Int. Cl. C07c 149/00, 43/18 US. Cl.260-609 R 19 Claims ABSTRACT OF THE DISCLOSURE [Cyclohexen- 3)-ylidene-methyl] -hydrocarbon ethers and thioethers and theircorresponding 2,5-endomethylene derviatives, preparation thereof andtheir use as anti-ozonants.

This invention relates to an anti-ozonant.

It is known that consumer goods obtained by vulcanisation frompolychloroprene develop cracks when their surface is under mechanicalstrain, whether through elongation, compression or shearing, and are atthe same time, exposed to the effects of ozone. Although the resistanceto ozone of products such as these is considerably higher than that ofproducts made of, for example, natural rubber or styrenebutadine rubber,it is still far from adequate in many cases. The service life ofpolychloroprene goods can be significantly increased by the addition tothe rubber in relatively small quantities of p-phenylene diaminederivatives such as, for example, N-phenyl-N'-isopropylp-phenylenediamine. Unfortunately, all the hitherto known effective compounds ofthis kind discolour under the effect of light so that they can only beused in articles containing carbon black. However, it is only possiblein some cases to use articles containing carbon black of the kind thatdo not discolour adjoining materials on contact therewith. It is alsoknown that certain wax combinations can be used to improve theresistance to ozone of light products. Although combinations such asthese do exert a certain protective effect, they will only produce thiseffect providing the film of protective wax formed over the surface ofthe object remains fully intact. Unfortunately, the film tears veryeasily under dynamic stress with the net result that the ozone-inducedcracks developed at these breaks in the film tend to be deeper and widerthan those formed in the absence of the wax film. Even when the Wax filmremains fully intact, protection is far from complete because a smallquantity of ozone still penetrates through the film and ultimately givesrise to the development of cracks.

We have now found that vulcanisates which are more resistant to ozonecan be obtained by using as antiozonants in rubber products containingat least 20% by weight of polychloroprene, based on the total polymercontent, compounds corresponding to the formulae:

and

"ice

represents oxygen (O--) or sulphur (-S), R and R each represent hydrogenor a methyl radical. One particularly significant technologicaladvantage of the compounds used in accordance with the invention is thatthey do not discolour.

The hydrocarbon radical R preferably consists of linear or branchedalkyl radicals with from 3 to 18, and preferably 4 to 12, carbon atomswhich may optionally be interrupted by hetero atoms such as for exampleoxygen or sulphur, aryl radicals, preferably phenyl and naphthyl, andaralykyl radicals, preferably containing phenyl as the aromaticcomponent and between 1 and 3 carbon atoms in the aliphatic chain, inwhich case the chain of the aralkyl radical may optionally be furtherinterrupted by a hetero atom, such as for example oxygen or sulphur.

The enolethers according to the invention may be prepared byconventional methods, for example, by reaction aldehydes with alcoholsor mercaptans in the presence of acids as catalysts to form thecorresponding acetals or thioacetals. The compounds formed in the firststage are converted in a second reaction stage into the correspondingenolor thioenolethers by heat treatment which is accompanied by theelimination of alchohol or mercaptan. Thioenolethers may also bedirectly formed from mercaptans and aldehydes provided the reaction iscarried out with a molar ratio of 1:1.

As a rule, the water formed during the acetal formation isazeotropically distilled off from a mixture of 1 mol of the aldehyde andat least 2 mols of an alcohol in the presence of catalytic quantities ofa strong acid such as p-toluene sulphonic acid, for example, by means ofan organic solvent which is immiscible with water such as, for example,chloroform, benzene, xylene or washing spirit or, optionally, by meansof an excess of the alcohol used.

After the water has been removed, the reaction mix ture is fractionatedthrough a column at reduced pressure to split up the acetal formed inthe first stage into alcohol and enol ether,

To prepare thioenolethers, a mixture of 1 mol of the aldehyde and 1 molof a mercaptan is dehydrated by azeotropic distillation in the presenceof catalytic quantitles of a strong acid such as, for example, p-toluenesulphonic acid, by means of an organic solvent such as, for example,chloroform, benzene, toluene, xylene or washing spirit, resultingdirectly in the formation of the enolethers. The thioenol ether is thenpurified by distillation. In addition to p-toluene sulphonic acid, {3-or ocnaphthalene sulphonic acid, orthophosphoric acid and polyphosphoricacids, for example, may also be used as the strong acids added incatalytic quantities in the preparation of enolethers andthioenolethers. It is of course also possible to use strongly acid ionexchangers for the purpose of acid catalysis.

The following compounds are mentioned by way of example as startingmaterials for the preparation of the enolethers according to theinvention: aldehydes such as A3 -tetrahydrobenzaldehyde,

A3-3 or 4-methyltetrahydrobenzaldehyde,A3-2-methyltetrahydrobenzaldehyde,A3-3,4-dimethyltetrahydrobenzaldehyde,A3-4-chlorotetrahydrobenzaldehyde,

A3-3 ,4-dichlorotetrahydrobenzaldehyde,

A3 -4-cyanotetrahydrobenzaldehyde,A3-2,5-endomethylenetetrahydrobenzaldehyde;

alcohols such as for example n-butanol, isobutanol, noctanol, i-octanol,i-nonylalcohol, n-dodecanol, benzyl al- 0 cohol, cyclohexanol,4-tert.butylcyclohexanol, 2-phenylethanol, 3-phenyl-propanol, ethyleneglycol monopropylether, ethylene glycol mono butylether, ethylene glycolmonohexylether, diethylene glycol monomethylether, diethylene glycolmonoethylether, diethylene glycol monobutylether;hydroxyalkylphenylethers such as, for example, 2-phenoxyethanol,2-(4-methylphenoxy)-ethanol; hydroxyethylalkyl or aryl sulphides such asfor example 1- hydroxyethylmethyl sulphide, -n-butylsulphide,-n-dodecylsulphide, -benzylsulphide, -phenyl sulphide,-[4-methylphenyl]-sulphide, [4 tert.-butylphenyl]-sulphide or mercaptanssuch as, for example, n-dodecyl mercaptan and 4- tert.-butylthiophenol.

Examples of the enolethers claimed in accordance with the inventioninclude [cyclohexen- 3 -ylidene-methyl] -n-butylether,

[cyclohexen- 3 -ylidene-methyl] -n-hexylether,

[3- (or -4 1nethylcyclohexen- 3 )-ylidene-methyl] -nhexylether,

[cyclohexen-(3 -ylidenemethyl] -i-octylether,

[3 (or -4- -ylidene-methyl] -i-nonylether,

octylether,

[3- (or -4) -methylcyclohexen- (3 -ylidene-methy1] benzylether,

[cyclohexen- 3 -ylidene-methyl] -benzylether,

[cyclohexen- (3 )-ylidene-methyl] -i-nonylether,

[cyclohexen- (3 )-ylidene-methyl -n-dodecylether,

[3- (or -4) -methylcyclohexen- 3 -ylidene-methyl] -ndodecyl thioether,

[3- (or -4) -methylcyclohexen- (3 -y1idene-methyl] -4-tert.

butylphenyl thioether,

[cyclohexen- 3 )-ylidene-methyl] -n-butyl-diethylene glycolether;

[cyclohexen- 3 -ylidene-methyl] -phenyl-ethylene glycolether;

[4-chlorocyclohexen- 3 )-ylidene-methyl] -n-hexylether,

[4-cyanocyclohexen- 3 )-y1idene-methyl]-i-octyl ether,

[3 ,4-dichlorocyclohexen-( 3 )-ylidene-methyl] -n-buty1- ether,

[Z-methylcyclohexen- 3 -y1idene-methyl] -benzylether,

[cyclohexen- (3 )-ylidene-methyl] -cyclohexylether,

[2,S-endomethylene-cyclohexen- 3 -ylidene-methyl] -nhexylether,

[2,5 -endomethylene-cyclohexen- 3 )-ylidene-methyl] -ioctylether,

[2,5 -endomethylene-cyclohexen- 3 -ylidene-methyl] -ndodecylether,

[2,S-endomethylene-cyclohexen- 3 -ylidene-methyl] benzylether,

[2,5 -endomethylene-cyclohexen- 3 -ylidene-methyl] -ndodecylthioether,

[cyclohexen- (3 -ylidene-methyl] [2-methyl-thioethyl1- ether and[cyclohexen- 3 -ylidene-methyl] [2-phenylthioethyl] ether.

The compounds used in accordance with the invention may readily bedistributed in rubber mixtures and may be used in conjunction with thechemicals normally used in rubber (for example, vulcanisationaccelerators, vulcanising agents, anti-agers, plasticisers, fillers,waxes, dyes and so on), without in any way affecting their specificactivity.

The novel products are used in the rubber in quantities of from 0.1 to6.0% by weight, and preferably in quantities of from 0.3 to 3.0% byweight, based on the content of polymer which consists of 100.0% byweight of polychloroprene or polychloroprene with a co-vulcanisablerubber, the minimum polychloroprene content being 20% by weight, andpreferably 30% by weight.

Examples of suitable co-vulcanisable rubbers include natural rubber orsynthetic rubber-like polymers which still contain double bonds, andwhich are obtained for example from conjugated diolefins such asbutadiene, dimethyl butadiene, isoprene and its homologues, orcopolymers of conjugated diolefins such as these with polymerisablevinyl compounds such as, for example, sty- 4 rene, a-methyl styrene,acrylonitrile, methacrylonitrile, acrylates and methacrylates.

The effect of the compounds used in accordance with the invention invulcanisates containing polychloroprene lies both in a higher level ofstabilisation against the effects of ozone and in a longer service lifeof rubber products exposed to the influences of ozone.

EXAMPLE 1 The following mixtures were prepared on mixing rolls:

Parts by wt. Polychloroprene 100.0 Magnesium oxide 4.0 Stearic acid 0.5

Precipitated silica (BET-surface 180 rn. g.) 20.0 Soft kaolin 170.0

Titanium dioxide 5.0 Antimony oxide 5.0 Chloroparaflin 10.0 Naphthenicmineral oil plasticiser 20.0 Paraflin 40 Zinc oxide 5.0 Ethylenethiourea 1.0 Anti-ozonant according to Table 1 1.0

Test specimens measuring 0.4 x 4.5 x 4.5 cm. were prepared from thesemixtures and vulcanised (press vulcanisation: 30 minutes at 151 C.).

Groups of four of the test specimens were then clamped in a plasticsframe in such a way that elongations of 10%, 20%, 35% and 60% weredeveloped over their surfaces. The test specimens were then treated witha stream of air containing 1000 parts of ozone to 100 mil lion parts ofair, at room temperature. Crack formation was then assessed at regularintervals as specified in the table set out below by counting the totalnumber of cracks formed that were visible with the naked eye, and alsoby measuring their average length in accordance with the followingsystem.

Number of cracks: Average length of the cracks:

No cracks No crack formation 0 1-2 cracks 1 Just visible 1 39 cracks 213 2 1924 cracks 3 3-8 mm. 3 25-79 cracks 4 More than 8 mm. 4 80249cracks 5 t More than 250 cracks 6 In the following table, the resultsobtained are separated by a vertical line with the number of cracksindicated first in each case. In the tables, the symbol means that thetest specimen broke.

TABLE I Hours 2 10 33 66 168 (a) No anti-ozonant present (b)[cyclohexen-(h)-ylidene-methyl]-n-butylether Elongation, percent:

10 0/0 0/0 0/0 0/0 0/0 0/0 0/0 O/0 O/0 0/0 0/0 0/0 0/0 0/0 0/0 60 0/00/0 0/0 1/3 l/4 (c) [3- (or4)-mcthylcycl0hexen-{3)ylidene-methyH-n-butylether Elongation, percent:

0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 35 0/0 0/0 l/2 l/4 l/4 0/0 4/24/4 TABLE IContinued Hours 2 10 33 66 168 (d) [eyclohexen- (3) -yl1denemethyl] -n-hexylether Elon atlon percent:

(e) [3- (or -4)-methy1cyclohexen-(3)-ylidene'n1ethyl] n-hexyletherElongation, percent:

(i) [cyclohexen-(3)-ylidene-methyl]ioctylether Elongation, percent:

(h) [3- (or -4)-methyleyclohexen-(3)-ylidene-methyl]-i-octyletherElongation, percent:

(i) [eyclohexen-(3)-y1idene-methy1] i nonylether E1 tion, ercent:

i in"? 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/01/1 1/3 1/4 (k) [cyclohexen-(B)ylidenemethyH-n-dodecylether Elon ation,ercent:

(l) [3- (or -4)-methyleyclohexen-(3)-ylidene-methyl]-n'dodeeylthioethe-Elongflation, percent:

(In) [3- (or 4)-methy1cyclohexcn-(3)qlidene-methyHA-tert.-butylphenylthloether Elon atlon, percent:

(n) [2,5-endomethylene-cyc1ohexen-(3)-ylidene-methyl]-n-hexylether Testspecimens measuring 0.4 x 4.5 x 4.5 cm. were prepared from thesemixtures and then vulcanised (press vulcanjsation 30 minutes at 151 C.).

This test was carried out as described in Example 1, the only differencebeing that 200 instead of 1000 parts of ozone were used to million partsof air. The results obtained are set out in Table 2:

TABLE 2 Hours 2 6 18 33 57 (a) No antl-ozonant present Elongation,percent:

EXAMPLE 3 The following mixtures were prepared on mixing rolls Parts bywt. Polychloroprene 35.00 Styrene-butadiene copolymer 65.00 Titaniumdioxide 10.00 Air-classified hard kaolin 30.00

Precipitated silica (BET-surface m. /g.) 20.00 Naphthenic mineral oilplastieiser 5.00 Stearic acid 1.00 Magnesium oxide 2.00 Zinc oxide 5.00Ethylene thiourea 0.25 Dicyclohexylamine 1.00 Dibenzothiazyl disulphide1.00 Tetramethyl thiuram monosulphide 0.20 Sulphur 1.40 Anti-ozonant cf.Table 3 0 and 2.00

Test specimens measuring 0.4 x 4.5 x 4.5 cm. were prepared from thesemixtures and vulcanised in a press for 30 minutes at 151 C.

The tests were carried out as in Example 2. The results are set out inTable 3:

TABLE 3 Hours 2 6 18 33 57 (a) Non anti-ozonant present Elongation,percent:

(b) [3'(or-4)-methylcyclohexen-(3)-y1idene-methy1]-n-dodecylthloetherElongjation, percent:

(c) [3-(or-4)-methylcyelohexen-(3)-ylidene-mcthy1]-n-octyletherElongation, percent:

Test specimens measuring 0.4 x 4.5 x 4.5 cm. were prepared from themixtures and vulcanised in a press for 30 minutes at 151 C.

The tests were carried out as described in Example 1, the onlydiiference being that 400 instead of 1000 parts of ozone were used to100 million parts of air. The results obtained are set out in Table 4.

TABLE 4 Hours 2 6 18 33 57 (a) No anti-ozonant present Elongation,percent:

(b) [cyclohexen-(3) -ylidene methyl]-benzy1ether Elongation, percent:

(c) [cyelohexen-(3)-ylidene-methyl] n-butyl ethylene glycol etherElongation, percent:

(d) [cycloheXcn-(3)-ylidene-methyl]-ethyl diethylene glycol etherElongation, percent:

(c) [cyclohexen-(3)-ylidnencmethyl]-phenyl ethylene glycoletherElongation, percent:

EXAMPLE 5 The compounds used in accordance with the invention may beprepared as follows:

(a) General method of producing enol others A mixture of 204 g. (2 mols)of n-hexanol-(l), 110 g. (1 mol) of tetrahydrobenzaldehyde and 200 ml.of toluene containing 1 g. of p-toluene sulphonic acid is heated for 3/2 hours on a water separator until it boils. Following elimination ofthe water present, the reaction mixture is distilled through a column tosplit up the acetal obtained as the first stage into alcohol andenolether. [Cyclohexene-( 3 )-ylidene-methyl]-n-hexylether is obtainedin a yield of 134 g.: colourless, thinly liquid oil of B.P. mm 123- 126C.

The enolethers set out in Table 5 are s1m1larly prepared:

TABLE 5 B.P. Alcohol Aldehyde Enolether C.)

l-butanol Tetrahydro- [Cyclohexen-(3)-yli 96-97/llolenizaldedene-methyll-n-butyl- 12 mm.

y e. er.

2-ethyl4-hcxanol do [Oyclohexen-(3)-yli- 141-142/ (i-octanol)dslrlie-methyll-i-octyl- 12 mm.

e er.

3,5,5-trimethyldo [Cyclohexen-(3)-yli- 151-152/ l-hexanol plusdcne-methyl1-i-nonyl- 12 mm. isomer (1- ether. nonyl alcohol).

l-dodecanol do [Cyclohexen-(ED-yll- 197-202/ dene-methyl]-n-do- 12 mm.decylether.

l-butanol Tetrahydro- [3-(or -4)-methylcyclo- 111-112/tolylaldehexen-(S) -ylidene- 12 mm. hyde. ene-methyl]-n-butyl ether.l-hcxanol do [3-(or -4)methylcyclo- 137-138] hexen-(3)ylidene- 12 mm.metbyH-n-hexylether.

2-cthyl-1hexanol do [3-(or -4)-methylcyclo- 153-154] (i-octanol).hexen-(3)-ylidene- 12 mm.

methyll-l-octylcther.

l-oetanol do [3-(or -4)-meth yleyclo- 163-168] hexen-(3)-yl1dene- 12 mm.methyH-n-octylether.

Benzy1alcoh0l Tetrahydro- [Oycl0hexen-(3)-y1i- 155-156/benzaldedene-InethyH-benzyl- 12 mm. hyde. ether.

Ethylene glycol do [Oyclohexen-(3)-yli- 140/12monobntyldene.methyl]-n-butylmm. ether. ethylene glycolether.

Diethylene glycol d0 [Cyclohexen-(3)-yli- 134435]monoethyldene-methyll-ethylene- 4.5 ether. diethylene glycolmm.

ether.

2-phenoxyethanol do [Cyclohexen-(3)-yli l6l/3.5

dene-rnetl1yl]-phenylmm. ethylene glycolether.

(b) General method of producing thioenol ethers A mixture of g. (0.75mol) of 4-tert.-butyl thiophenol, 93 g. (0.75 mol) of tetrahydrotolylaldehyde and 150 ml. of xylene containing approximately 0.5 g. ofptoluene sulphonic acid is heated for 4 hours on a water separator untilit boils. Following removal of the water, the reaction mixture isfractionated twice under a high vacuum. {3 (or-4)-methylcyclohexen-(3)-ylidene-methyl]-4-tert.-butyl phenylthioetheris obtained in a yield of 58 g.; yellowish oil of B.P. 02 mm 157-168 C.

A mixture of 202 g. (1 mol) of n-dodecyl mercaptan, 124 g. (1 mol) oftetrahydrotolyl aldehyde and 200 ml. of xylene containing approximately0.5 g. of p-toluene sul phonic acid is heated for 4 hours on a waterseparator until it boils. Following removal of the water, the reactionmixture is distilled under a high vacuum. [3-(or-4)-methylcyclohexen-(3)-ylidene-methyl] n dodecylthioether is obtainedin a yield of 213 g.; yellowish oil of B.P. 182-188 C.

(c) Production of [2,5-endomethylene-cyclohexen-(3)- ylidenemethyl]-n-hexylether A mixture of 306 g. (3 mols) of n-hexanol-(l), 124 g. (1mol) of 2,5-endomethylene-tetrahydrobenzaldehyde and 250 ml. of toluenecontaining 1 g. of p-toluene sulphonic acid and 1 ml. of pyridine isheated for one hour on a water separator until it boils. Following theremoval of the water, the reaction mixture is distilled through a columnto split up the acetal obtained as the first stage into alcohol andenolether. The fraction distilling over at 121-130 C./ 12 mm. Hg is thenfractionated through a column to give 133 g. of[2,5-endomethylene-cyclohexen-(3)-ylidenemethyl]-n-hexylether in theform of a colourless, thinly liquid oil of B.P.lg 133 C.

Other 2,S-endomethylene-cyclohexen-(3)-ylidene-methylethers orthioethers can be obtained by similarly reacting2,S-endomethylene-tetrahydrobenzaldehyde with 1- butanol,2-ethyl-1-hexanol, 3,5,5-trimethyl-l-hexanol and isomers, n-octanol-(1), n-dodecanol-(l) or benzyl alcohol; or with alkylated benzyl alcoholssuch as, for example, 3-methyl-benzyl alcohol, or withhydroxyalkylphenylethers such as 2-phenoxy-1-ethanol orl-phenoxy-Z-proand wherein R is hydrocarbon containing from 3 to 18carbon atoms or alkyl containing 3 to 18 carbon atoms interrupted 'by aO or S- moiety, X is -O- or S and R and R are each selected from thegroup consisting of hydrogen and methyl.

2. Compounds of the formula wherein R is hydrocarbon containing from 3to 18 carbon atoms, X is -O or --S- and R and R are each selected fromthe group consisting of hydrogen and methyl.

3. Compounds of the formula wherein R is phenylalkyl containing between1 and 3 carbon aatoms in said alkyl moiety, X is --O- or -S- and R and Rare each selected from the group consisting of hydrogen and methyl.

4. [Cyclohexen-(3)-ylidene-methyl]-n-butylether.

5. [3- (or -4)-methylcyclohexen (3) ylidene-methyH- n-butylether.

6. [Cyclohexen- (3 )-y1idene-methyl] -n-hexylether.

7. [3 (or -4)-methylcyclohexen (3) ylidene-methyl]- n-hexylethe'r.

8. [Cyclohexen- (3 -ylidene-methyl] -i-octylether.

9. [3 (0r -4)-methylcyclohexen-(3)-ylidene-methyl]- n-octylether.

10. [3 (or 4-methylcyclohexen-(3)-ylidene-methyl]- i-octylether.

11. [Cyclohexen-( 3 -ylidene-methyl] -i-nonylether.

12. [Cyclohexen-(3)-ylidene-methyl]-n-dodecylether.

13. [3 (or -4)-rnethylcyclohexen-(3)-ylidene-methyl]-n-dodecylthioether.

14. [3 (or -4) methylcyclohexen-(3)-ylidene-methyl]- 4-tert.-butylphenylthioether.

15. [Cyclohexen- (3 -ylidene-methyl] -benzylether.

16. 2,5 endomethylene-cyclohexen-(3)-ylidene-methyl] -n-hexylether.

17. [Cyclohexen-(3)-ylidene-methyl] n butyl-ethylene glycol ether.

18. [Cyclohexen-(3)-ylidene-methyl] ethyl-diethylene glycol ether.

19. [Cyclohexen-(3)-ylidene-methyl] phenyl-ethylene glycol ether.

References Cited UNITED STATES PATENTS 2,487,525 11/1949 Copenhaver260611 FOREIGN PATENTS 730,732 3/1966 Canada 260611 697,905 9/1953 GreatBritain 260611 BERNARD HELFIN, Primary Examiner US. Cl. X.R.

252406, 407; 26045.7 R, 45.7 S, 611 A, 611 F, 611R

